libgo/go/go/doc/synopsis.go

   1 // Copyright 2012 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package doc
   6
   7 import (
   8         "strings"
   9         "unicode"
  10 )
  11
  12 // firstSentenceLen returns the length of the first sentence in s.
  13 // The sentence ends after the first period followed by space and
  14 // not preceded by exactly one uppercase letter.
  15 //
  16 func firstSentenceLen(s string) int {
  17         var ppp, pp, p rune
  18         for i, q := range s {
  19                 if q == '\n' || q == '\r' || q == '\t' {
  20                         q = ' '
  21                 }
  22                 if q == ' ' && p == '.' && (!unicode.IsUpper(pp) || unicode.IsUpper(ppp)) {
  23                         return i
  24                 }
  25                 ppp, pp, p = pp, p, q
  26         }
  27         return len(s)
  28 }
  29
  30 // clean replaces each sequence of space, \n, \r, or \t characters
  31 // with a single space and removes any trailing and leading spaces.
  32 func clean(s string) string {
  33         var b []byte
  34         p := byte(' ')
  35         for i := 0; i < len(s); i++ {
  36                 q := s[i]
  37                 if q == '\n' || q == '\r' || q == '\t' {
  38                         q = ' '
  39                 }
  40                 if q != ' ' || p != ' ' {
  41                         b = append(b, q)
  42                         p = q
  43                 }
  44         }
  45         // remove trailing blank, if any
  46         if n := len(b); n > 0 && p == ' ' {
  47                 b = b[0 : n-1]
  48         }
  49         return string(b)
  50 }
  51
  52 // Synopsis returns a cleaned version of the first sentence in s.
  53 // That sentence ends after the first period followed by space and
  54 // not preceded by exactly one uppercase letter. The result string
  55 // has no \n, \r, or \t characters and uses only single spaces between
  56 // words. If s starts with any of the IllegalPrefixes, the result
  57 // is the empty string.
  58 //
  59 func Synopsis(s string) string {
  60         s = clean(s[0:firstSentenceLen(s)])
  61         for _, prefix := range IllegalPrefixes {
  62                 if strings.HasPrefix(strings.ToLower(s), prefix) {
  63                         return ""
  64                 }
  65         }
  66         return s
  67 }
  68
  69 var IllegalPrefixes = []string{
  70         "copyright",
  71         "all rights",
  72         "author",
  73 }